feat: Solve course-schedule problem

Author: hu6r1s

course-schedule/hu6r1s.py

@@ -0,0 +1,37 @@
+from collections import defaultdict
+
+class Solution:
+    # def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+    #     for pre_x, pre_y in prerequisites:
+    #         if [pre_y, pre_x] in prerequisites:
+    #             return False
+    #     return True
+
+
+    def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+        d = defaultdict(list)
+
+        for x, y in prerequisites:
+            d[x].append(y)
+        
+        visited = set()
+        finished = set()
+
+        def dfs(course):
+            if course in visited:
+                return False
+            if course in finished:
+                return True
+
+            visited.add(course)
+            for v in d[course]:
+                if not dfs(v):
+                    return False
+            visited.remove(course)
+            finished.add(course)
+            return True
+
+        for course in list(d):
+            if not dfs(course):
+                return False
+        return True